Some conventional selective call receivers apply partial address correlation on all intercepted messages transmitted by a radio communication system in order to extend the battery life of the selective call receiver. Partial address correlation is performed by collecting a portion of the address field included in an intercepted message, and determining if the portion of the address field possibly matches with any number of predetermined selective call addresses stored in the selective call receiver. An address match is determined from a partial address match of less than a predetermined number of bit differences. If a partial address match is found, the selective call receiver intercepts the complete message. If a partial address match is not found, the receiver circuit is shutdown early to conserve energy and extend battery life.
Although partial address correlation generally requires additional processing resources, partial address correlation produces a net energy savings when compared to traditional address decoding schemes that maintain the receiver circuit on for the duration of the address field. This is because the energy consumed by the receiver circuit is a significant portion of the overall energy consumed by the selective call receiver. Thus, early shutdown of the receiver circuit provides substantial energy conservation, thereby extending battery life.
Partial address correlation provides battery life savings in cases where the number of selective call addresses stored in the selective call receiver is small and the data included in the intercepted messages is random. Each of these cases result battery life savings, because the overall probability that the selective call receiver will find a partial address match is low, and the likelihood of early receiver circuit shutdown is high.
However, as the number of selective call addresses is increased the probability of finding a partial address match increases, and the number of occurrences of early receiver circuit shutdown is reduced. Moreover, a higher number of selective call addresses results in a greater number of address comparisons, which increases the processing time for performing partial address correlation.
The less frequent shutdown of the receiver circuit combined with higher processing time diminishes the savings obtained from the application of partial address correlation. In addition, for a high number of address comparisons, a point is reached where the selective call receiver consumes more energy (on average) when applying partial address correlation than if traditional address decoding is used.
Thus, what is needed is a method and apparatus that can improve the battery life savings of selective call receivers applying partial address correlation.